This invention relates to collapsible automobile steering assemblies and, more particularly, to automobile steering assemblies having a spring-biased component.
In modern safety technology directed to the protection of automobile drivers from injuries caused by striking the steering wheel or steering wheel hub in case of a crash, the object, consistent with the legal requirement for drivers to use a safety belt, is to entrust restraint of the forward motion of the driver relative to the vehicle to the safety belt and to create a free space ahead of the driver to accommodate a braking motion of the driver within the seal belt restraint by causing the steering wheel as well as the steering column to retract in the event of a cash. Early examples of this kind of structure are disclosed in U.S. Pat. No. 3,791,233 and in German Offenlegungsschrift No. 24 08 174, which is the starting point of the present invention.
In the steering wheel structure described in the Offenlegungsschrift, a lower steering column tube part bears against the fire wall of the vehicle and an upper steering column part has a lower, piston-like end extending into a cylindrical region of the lower steering column part. A helical spring is arranged to urge the upper part in the direction of further penetration into the lower steering column part. The piston-like portion of the upper steering column part is normally held in place in the lower steering column part by locking pins which are broken by the action of additional forces on the piston-like end which are released by a collision switch at the instant of the crash. As a result, the action of the spring causes a shortening of the steering column together with the desired retraction of the steering wheel away from the driver.
In place of the relatively costly solution utilizing a collision switch, one arrangement described in the Offenlegungsschrift uses the combined inertia of the upper steering column part and the steering wheel to break the shear pins. However, this solution is unreliable since force components transverse to the axis of the steering column occur in a crash because of the inclination of the column and, accordingly, the danger of tilting of the column is present.
Because of the fixed support for the lower parts of the steering column and steering column tube on vehicle elements which are displaced towards the driver in the case of a crash, such vehicles are unable to provide free space to accommodate a braking motion of the driver when the front of the vehicle is deformed in such a manner. Because of the tilting of the column, the full release path of the spring will not be available to increase the distance between the steering wheel and the driver. Instead, the steering wheel retraction is reduced by the length of the displacement of the point of support of the column, in particular of the lower steering column part.